Current Questions & Answers

MEMBER'S QUESTION:

What do you know about ECT 24 replacing ECT 32 ? How would that be possible and what liners? Maybe replacing 150 mullen? What liner weights are used? Were the liner weights 35#. Doesn't 35# liners gets us to 32# now ??

ASKRALPH! RESPONDS:

In the Degradation Study started during the summer of 2008, and has continued to remain open, we  found several converters that have actually shipped boxes with ECTs below the 32# . These were  post press samples that were sent  that may or may not have been above a 32# ECT as incoming sheets. Since these "boxes" did not fail in the field (that we know of) one could assume that  these combined boards in the low twenties have actually substituted for what was described as 32# ECT. It all goes back to knowing your customers' needs.

Using 35# liners does not quaratee combined board performance.  Basis weights are not a good indicator of box performance! If one doesn't bond the components properlyt on the corrugator, flute the medium properly and crush the combined sheet in the converting operation ECT and box performance suffer.  There is a big difference between the potential in the roll stock and the finished product. 

MEMBER'S QUESTION:
Here is my new question. How do I test the paper to be sure that the board combo weights are correct ? If we order a board combination of 42-26-42 how can I verify that the correct paper weights were used ? What test equipment and TAPPI standard should I use.

Thanks again for all your help.

ASKRALPH! RESPONDS:

Thank you for an easy to answer and  another good question this time.

The TAPPI test method for a basis weight analysis is “Grammage of Paper and Paperboard T-410”.  You will need to gently soak the sample apart in some warm water until the three components have separated from each other.  Take a single edge razor blade and gently scrape off the starch from the liners and the medium.  Be careful not to remove fibre.

The samples will need to be dried to 7 percent moisture. You will then need to measure the dimensions of the sample and then convert the weight per sample size into pounds per thousand square feet for the three components.  You can use an inexpensive scale to measure the weight of the samples.

Or, I could recommend an outside lab.  Surprise visits to your sheet suppliers to view the roll stock inventory and check production records and purchasing logs is always a good idea.

MEMBER'S QUESTION:

We have a customer that is currently using a 32 ECT RSC and would like to transition to an HSC for cost savings.  They are under the impression that they will need to upgrade the board construction to maintain the same performance.  Do you have any ideas, data, etc. that does or does not support that theory?

 

Thank you for your help,

 

ASKRALPH! RESPONDS:

 

Now that’s a great question.  The simple answer is that the compression strength of a corrugated box is a product of the ECT strength in the side walls and the flexural stiffness of the vertical panels.  The flaps on a corrugated box are “relatively” useless as far as box performance goes.  Flexural stiffness can be measured, but is highly dependent on the caliper of the combined board.

 

So as long as the dimensions of the box and ECT strength from the combined components do not change than there should not be a performance difference between a RSC and HSC.

 

My source for this information is George Maltenfort’s two books: Corrugated Shipping Containers and Performance and Evaluation of Shipping Containers.  I can send you a pdf of a few pages, but they are rather technical in nature with an engineering perspective.  And, we can always sent the two designs out to an independent lab for evaluation.

MEMBER'S QUESTION:

I am ready to quote on a substantial new piece of business.  The potential customer's specs include both basis weights combinations and minimum top-to-bottom compression.  I will send you my competitors boxes so that they can be evaluated.  Please get back to me with your recommendations.

ASKRALPH! RESPONDS:

As promised here the range in ECT values based on the AF&PA Continuous Containerboard Data Report.  I have taken the CD ring crush values for the grades listed in the spec sheet and calculated the ECTs based on the high and low ring crushes for each grade.  These have not been reviewed by another set of eyes, so tell me if these values do not seem correct to you.  I was also very impressed by the packer’s specification for minimum compression values and not just board combinations with a reference to basis weights.